全球衛星定位系統(GPS)目前已廣泛地運用於導航及測量的領域之中，雖然一般民用受限於公尺級的精確度，但隨著多年發展，越來越低價的接收儀器，並配合使用相關輔助方法(差分修正法及載波相位平滑化法等等)，已可獲得公分等級之精確度，由此可見，GPS的應用範圍可更進一步的推廣。
本研究之目的即為使用較低價、易於取得之簡易型GPS接收儀器，證明普通的導航接收器亦可確實提昇其精確度；精心設計由一輛玩具車自一斜坡上滑下之多合一實驗，探討分析作用其上之數種力(包含磨擦力)，進而量測出因地球重力所產生玩具車之加速度值。
由實驗結果可顯示出GPS運用在地球重力場的量測方面之高度潛力，實驗中透過cycle-slip篩檢衛星資料、差分修正法以及載波相位平滑化法處理資料後，即可求得被測物體之垂直加速度，證實了即使僅用低價位單頻之GPS 導航接收儀器，亦可達到10 公分/秒2等級精確度之要求。

The Global Positioning System (GPS) has already been widely applied to the navigation and surveying areas at present time. Even though the general accuracy is limited to the level of meters, as a result of many years research development, the more low-cost receivers coped with the auxiliary methods (e.g. differential Global Positioning System (DGPS) and phase smoothing techniques, etc.) can achieve the centimeter accuracy. As a result, The GPS applications can be expanded into more areas.
The main purpose of this study is to initiate an application of a low-cost and simple GPS receiver to prove that the accuracy level of a common navigation receiver can be improved. The studied application is to measure the acceleration due to the Earth gravity. In accomplish that, this research started with the design of a slope sliding with a toy car. The forces (including friction force) acting on the car were carefully analyzed. Several experiments were conducted.
The results show that the potential of GPS application to measure Earth gravity is high. This research proves that even with a low-cost single-frequency GPS navigation receiver, an accuracy of 10 centimeters/sec2 can be achieved. The experiment design and the data processing with cycle-slip detection, DGPS, and phase smoothing techniques have been proved to be capable of sensing vertical acceleration.

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